Plan B - could I be pregnant after taking morning after pill ?

hi I had sex on a wed then on a Friday (unrotected) then took the morning after pill on the Friday (same day as 2nd time sex)a week later had a period now it's 3 weeks later and I'm getting pregnancy symptons lower back pain feeling dizzy and sick tingling in pelvic bone area . I allready have to children but I'm still really not sure if could be preg